1. Field of the Invention
The present invention relates to an ink jet apparatus and a method for controlling the ink jet apparatus.
2. Description of the Related Art
Ink jet apparatuses that form an image on an object to be printed on, using an ink jet head discharging a liquid from a plurality of discharge ports, have been widely used. The ink jet apparatuses change the volume of a pressure chamber communicating with a discharge port to thereby discharge the liquid stored in the pressure chamber from the discharge port. As a type in which the volume of the pressure chamber is changed, there is a type using an actuator that displaces a wall surface of the pressure chamber. A type using a piezoelectric element or the like as the actuator is referred to as a piezoelectric type, and a type using an electrostatic actuator is referred to as an electrostatic type. In addition, hereinafter, the discharge port, the pressure chamber, and the actuator are also collectively referred to as a nozzle.
In such ink jet apparatuses, an abnormality may occur in the nozzle such that bubbles are generated within the discharge port or the pressure chamber, or a contaminant adheres to the inside of the discharge port or the pressure chamber. In this case, a printing failure may occur such that the nozzle is clogged or the liquid is not discharged, or the liquid is discharged in directions different from usual. In order to reduce such a printing failure, there are known ink jet apparatuses that have the function of recovering the nozzle to a normal state when the state of the nozzle is determined and an abnormality has occurred in the nozzle.
For example, in an ink jet apparatus using actuators, it is known that a vibration pattern of damped vibration called residual vibration generated in an actuator immediately after the actuator is driven to displace a wall of a pressure chamber changes according to the state of a nozzle. Since a voltage applied to the actuator changes if the actuator vibrates, it is possible to detect this voltage to thereby determine the state of the nozzle from the detected voltage.
However, since a determination circuit that detects the voltage applied to the actuator to determine the state of the nozzle is relatively large, if the determination circuit is provided at every nozzle in order to determine the state of each of a plurality of the nozzles, the size of the ink jet apparatus becomes too large.
In contrast, in order to reduce the size of the ink jet apparatus, ink jet apparatuses that determine the state of a plurality of nozzles, using one determination circuit, are disclosed in International Publication No. WO2004/076180 and Japanese Patent Application Laid-Open No. 2005-305992.
The ink jet apparatus described in International Publication No. WO2004/076180 has a switch to connect an actuator to a drive circuit outputting a driving current for driving the actuator or to a determination circuit that determines the state of a nozzle. In this ink jet apparatus, after a driving current is supplied from the drive circuit to the actuator, the switch is switched to connect the actuator to the determination circuit to detect a voltage applied to the actuator. In addition, the ink jet apparatus having one switch common to all nozzles is disclosed in FIG. 27 of International Publication No. WO2004/076180, and the ink jet apparatus having a plurality of switches corresponding to the nozzles, respectively, is disclosed in FIG. 30.
Additionally, in the ink jet apparatus described in Japanese Patent Application Laid-Open No. 2005-305992, one end of each of a plurality of actuators is connected to a drive circuit that outputs a driving signal, and the other end of the actuator is connected to a residual vibration detection circuit that detects residual vibration from a voltage applied to the actuator. In addition, the residual vibration detection circuit determines the state of a nozzle from a vibration pattern of the detected residual vibration. Additionally, in this ink jet apparatus, one switch is provided between the plurality of actuators and the residual vibration detection circuit, and it is possible to connect the plurality of actuators to one residual vibration detection circuit.
However, the ink jet apparatus disclosed in FIG. 27 of International Publication No. WO2004/076180 has a problem in that the operating speed of the ink jet apparatus decreases when the apparatus has a large number of nozzles.
In this ink jet apparatus, a driving current for driving a plurality of nozzles flows to a switch that connects actuators to the drive circuit. Since this driving current becomes larger as the number of nozzles to be driven increases, when a large number of nozzles are driven, an analog switch capable of handling a high current is required.
However, this ink jet apparatus should connect the determination circuit and an actuator to detect the voltage of the actuator immediately after a driving current is passed, and then connect the drive circuit and the actuator again until a driving current is output. For this reason, the analog switch needs to start a switching operation sufficiently earlier than the head of the driving signal of the drive circuit, and complete the switching operation before the head of the driving signal to pass the current of the driving signal therethrough. Additionally, the analog switch needs to start a switching operation at a rear end of the driving signal and determine the state of a nozzle through the determination circuit after the completion of the switching operation. When the state of the nozzle is determined by the determination circuit after the completion of the switching operation at the rear end of the driving signal, there is a problem in that the residual vibration is already attenuated and precise determination is difficult.
Allowance of the precise determination is limited to an ink jet nozzle designed so that the residual vibration of an actuator lasts a relatively long time. However, it is difficult for the ink jet nozzle in which the residual vibration of the actuator lasts a long time to be driven at a high frequency. Moreover, since the analog switch should start a switching operation sufficiently earlier than the head of the driving signal of the drive circuit, the driving signal is unable to be sent in a short cycle. Therefore, the operating speed of the ink jet apparatus decreases.
In contrast, it is considered that an analog switch with a fast operating speed is used by dividing actuators into a plurality of groups and driving the actuators in a time-sharing manner for every group to make the driving current small.
However, in the ink jet apparatus illustrated in FIG. 27 of International Publication No. WO2004/076180, a portion of a wiring line connecting an actuator to the drive circuit and a portion of a wiring line connecting the actuator to the determination circuit are shared. For this reason, it is necessary to provide most of the drive circuit driving the actuators for every group, and the scale of the circuit increases.
Additionally, in the ink jet apparatus disclosed in FIG. 30 of International Publication No. WO2004/076180, the plurality of switches are provided corresponding to the actuators, respectively. Therefore, it is possible to drive the actuators at a high speed. However, since a large-scale circuit that generates signals for switching the switches apart from a circuit that generates signals for driving the actuators is required, the circuit scale increases.
Additionally, in the ink jet apparatus disclosed in Japanese Patent Application Laid-Open No. 2005-305992, the residual vibration detection circuit and the actuators are unable to be individually connected to each other or disconnected from each other. For this reason, in this ink jet apparatus, the actuators should be driven one by one only in order to detect a voltage according to residual vibration apart from printing processing, and the operating speed of the ink jet apparatus decreases.
In addition, in the ink jet apparatus in Japanese Patent Application Laid-Open No. 2005-305992, the potential of one end on a grounding side of an actuator connected to the residual vibration detection circuit is detected by being isolated from the grounding side during residual vibration detection. For this reason, this method also has a problem in that the application range thereof is limited to an ink jet apparatus of the structure capable of electrically isolating one end on the grounding side of the actuator from the other.